why cant we leave well enough alone?

We can put the same orniments on a Christams tree year after year but we can't put one used part back on a motor. New senders, new dist' new wires, new belts, new hoses, and on and on. Cam will mean timing set, water pump, possible new radiator, etc..
A year later the bottom end comes apart. We can consider the new bottom end as a new tree. We might reluctently put some of those slightly used orniments on it.
If this is a sickness there isn't a pill for it. Good luck